Only by modifying the core files.
uddeIMshowMessage (inbox.php) displays the message. In the lower third of the function you will find an if-clause with "uddeIMdrawWriteform" inside. This can be moved above "// output the message" but you also have to move "$replytoid = $displaymessage->id;" because it is required inside the if-clause.
uddeIM & uddePF Development
CB Language Workgroup
CB 3rd Party Developer